Turbulence-induced size redistribution of submicron NaCl aerosols in ribbed confined flows prior to electrostatic collection

Submicron aerosols are difficult to collect electrostatically, motivating passive upstream conditioning that shifts particles toward more readily captured size ranges. This study presents a controlled, geometry-resolved experimental comparison linking rib-induced flow structures, NaCl aerosol size redistribution, and downstream electrostatic collection. Eight confined-channel rib configurations were evaluated under identical operating conditions using planar particle image velocimetry and size-resolved number measurements with the electrostatic precipitator deactivated and activated. Rib geometry governed flow separation, recirculation, transverse motion, and turbulence intensity. The zig-zag configuration without a center gap produced the strongest coupled recirculation and transverse interaction and the clearest redistribution signature: depletion of 0.3–0.8 μm particles accompanied by enrichment near 1.1 μm. Peak local turbulence intensity alone did not predict performance; coherent recirculation and transverse transport were more informative. With electrostatic activation, this best-performing geometry increased the collection efficiency of 0.3 μm aerosols from approximately 15% in the smooth channel to nearly 50%. These results establish an experimental link between rib-resolved flow organization, apparent size redistribution, and enhanced submicron aerosol collection.